1. Field of the Invention
The present invention relates to a buffer amplifier, and more particularly, to a rail-to-rail push-pull buffer amplifier and a source driver with such buffer amplifier application.
2. Description of the Related Art
In an electronic circuit, a buffer amplifier usually is used to transmit a signal to a terminal and to drive the next stage circuit. For example, in a liquid crystal display, a source driver comprises a buffer amplifier to apply an analog voltage required for the liquid crystal display to the liquid crystal display. The buffer amplifier, therefore, is an essential device in the source driver. An excellent buffer amplifier provides high-speed operation and accuracy. In the application of a portable device, such as a notebook or a personal digital assistant, power consumption is the most concerned issue of a buffer amplifier.
U.S. Pat. No. 6,331,846 discloses an operational amplifier which removes offset of the circuit. The prior art comprises complicate circuits, frequently switching signal routes to achieve its objects. The prior art circuit, however, results in high costs of the circuit, and the frequently switching the signal routes also generates noises.
In addition, U.S. Pat. No. 6,137,360 discloses a voltage follower with a rail-to-rail buffer amplifier. Although the offset-removing mechanism is not required, the charging rate and discharging rate are not equal in the prior art technology while the next stage circuit is driven.